This invention relates to the area of testing soil beneath storage tanks to determine if there are any leaks in the storage tank.
One of the most common ways of storing hydrocarbon, such as crude oil, gasoline and so forth is in large steel storage tanks which are normally cylindrical shape with the bottom resting on the soil. The particular soil is usually some material which will be least likely to cause corrosion of the bottom. This material includes clean river sand or clean washed crushed rock. Many precautions are made to improve the engineering of these tanks to prevent them from leaking. However, despite all of this effort these tanks do develop leaks. These leaks are harmful in at least two ways: (1) They can cause pollution of the underground soil and possibly underground water sources; and (2) the loss of the material itself is loss of a natural resource and this can also be costly in terms of dollars. For example, if one tank leaks more than two barrels of gasoline per day the loss would be more than 30,000 gallons per year. These tanks may be 100 to 200 feet in diameter and may contain upward to 100,000 or more barrels of fluid. If there are 25 such tanks in a tank farm then there could be a leakage of as much as 750,000. to 2,000,000 gallons of gasoline per year. There is presently no reliable way of detecting leaks under and in the bottom of these large tanks and further no way of determining the actual location or of repairing them while the tank is in service.